Position control device

Abstract

A position control device capable of maintaining high command follow-up performance even when a plurality of backlash portions exist in a torque transmission path. The position control device of the target plant 100 temporarily operates the target plant 100 so as to reverse the direction of travel with backlash compensation turned off, and detects the position detection value X of the load end 104. L and the position command value X at the timing when the position deviation DIF between the position command value X and the backlash portion BL k For each, the coefficient M for inversion detection k and a coefficient calculation unit 10 for calculating the coefficient M k , the position command value X, and the moment of inertia J of the entire load L Based on this, the load side transmission torque τ Lk a reversal detector 12 that detects the timing at which the backlash compensation value X BLc and a compensation value calculation unit 13 that increases or decreases the value.

Description

[Technical Field]

[0001] This specification discloses a position control device for a target plant in which a backlash portion exists in a torque transmission path from a motor. [Background technology]

[0002] Conventionally, a position control device that controls a motor so that the position of a target plant (hereinafter referred to as a "load position") follows a position command value has been widely known. Such a position control device is applied to, for example, axis control of a numerically controlled machine.

[0003] Here, backlash may exist in the torque transmission path between the motor and the target plant. The backlash is a gap or deflection between torque transmission members. This backlash becomes a dead zone where torque is temporarily not transmitted when the direction of motion is reversed. This backlash then causes a command tracking error.

[0004] Therefore, techniques for eliminating command tracking errors caused by backlash have been proposed in the past. For example, Patent Document 1 discloses a correction device that corrects backlash that occurs between a drive gear and a driven gear. The correction device in Patent Document 1 calculates a transmission torque applied from the drive gear to the driven gear based on position command information. When the sign of this transmission torque is reversed, the correction device determines that backlash has occurred and corrects the command value to correct the backlash. This technique can reduce command tracking errors caused by backlash to a certain extent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-366230 Summary of the Invention [Problem to be solved by the invention]

[0006] However, depending on the configuration of the torque transmission path, there may be multiple backlash parts instead of just one. Conventional techniques such as those disclosed in Patent Document 1 cannot handle such cases where there are multiple backlash parts in the torque transmission path. As a result, with conventional techniques, command follow-up performance is reduced when there are multiple backlash parts in the torque transmission path.

[0007] Therefore, this specification discloses a position control device that can maintain high command follow-up performance even when a plurality of backlash portions exist in the torque transmission path. [Means for solving the problem]

[0008] The position control device disclosed in this specification is a position control device for a target plant in which a motor and a load end are connected via a torque transmission path having a plurality of backlash sections, and is characterized by comprising: a coefficient calculation unit that calculates a reversal detection coefficient for each of the plurality of backlash sections based on the position command value at a timing when a position deviation between a position detection value of the load end and a position command value suddenly increases, or the speed command value and the acceleration command value at the timing when the position deviation suddenly increases, with backlash compensation turned off; a reversal detection unit that operates the target plant with backlash compensation turned on, and detects the timing when the load-side transmission torque at each of the plurality of backlash sections suddenly reverses, based on the reversal detection coefficient, the position command value, and the moment of inertia of the entire load; a compensation value calculation unit that increases or decreases a backlash compensation value at the timing when the load-side transmission torque suddenly reverses; and a position control loop unit that controls the position of the motor so that the position detection value of the load end becomes the position command value after being corrected with the backlash compensation value.

[0009] In this case, the compensation value calculation unit may add or subtract the backlash amount of the kth backlash portion, counting from the motor, to or from the current backlash compensation value at the timing when the load-side transmission torque reverses at the kth backlash portion.

[0010] The position control loop unit may control the position of the motor so as to reduce the absolute value of a position error, which is the difference between the compensated position command value and a position feedback value, and the position feedback value may include a value obtained by adding the position detection value of the load end and the backlash compensation value.

[0011] The position command value in the trial operation is a sine wave expressed by X=X0+R0×sinθ, and the coefficient calculation unit calculates θ when the position deviation increases suddenly due to the k-th backlash portion counted from the motor as θ k The moment of inertia of the entire load is J L Then, the coefficient M corresponding to the k-th backlash portion is k , M k =(sinθ1 / sinθ k )×J L It may be calculated based on the following.

[0012] The compensation value calculation unit calculates the load-side transmission torque at the k-th backlash portion as τ Lk , the sliding friction torque is τ F , when the acceleration command value is A, τ Lk =M k ×A+τ F In the equation, the load side transmission torque τ Lk may be calculated.

[0013] Further, the position command value in the trial operation is a sine wave expressed by X=X0+R0×sinθ, and the coefficient calculation unit calculates the acceleration command value when the position deviation suddenly increases due to the k-th backlash portion counted from the motor as A k Then, the coefficient N corresponding to the k-th backlash portion is k , N k=sgn(V k ) / A k It may be calculated based on the following formula:

[0014] Furthermore, the compensation value calculation unit calculates a determination parameter r when the speed command value is V, the acceleration command value is A, and the sign function is sgn. Lk , r Lk =-A×N k +sgn(V), and the determination parameter r Lk The timing at which the sign of the signal k is reversed may be detected as the timing at which the load-side transmission torque at the k-th backlash portion is reversed. [Effects of the Invention]

[0015] According to the technology disclosed in this specification, high command follow-up performance can be maintained even when a plurality of backlash portions exist in the torque transmission path. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a block diagram showing the configuration of a position control device. [Figure 2] FIG. 1 is a schematic diagram of a target plant. [Figure 3] 10A and 10B are diagrams illustrating an example of changes in a position command value, an acceleration command value, and a sliding friction torque. [Figure 4] 4 is a diagram showing changes in the position command value, torque, and position deviation in the range Sa of FIG. 3. FIG. [Figure 5] FIG. 1 is a schematic diagram of a target plant having only one backlash portion. [Figure 6] 6 is a diagram showing changes in a position command value and torque in the target plant of FIG. 5. FIG. [Figure 7] FIG. 10 is a block diagram showing another example of a position control device. DETAILED DESCRIPTION OF THE INVENTION

[0017] The configuration of the position control device will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the position control device. FIG. 2 is a schematic diagram of a target plant 100. As shown in FIG. 2, the target plant 100 has a motor 102, a torque transmission path 110, a load end 104, and a current control unit 120. The output torque of the motor 102 is transmitted to the load end 104 via the torque transmission path 110. The position control device controls the position X of the load end 104 according to a position command value X commanded from a higher-level device (not shown). L In order to control the torque command value τ of the motor 102, m The current control unit 120 calculates the torque command value τ m A current corresponding to the input voltage is applied to the motor 102. The current control unit 120 includes, for example, an inverter. Such a position control device is applied to, for example, axis control of a numerically controlled machine (e.g., a machine tool) or a robot. Such a position control device is required to have system stability and high command tracking performance.

[0018] As shown in FIG. 2, there are multiple (two in the illustrated example) backlash portions BL1 and BL2 in the torque transmission path 110 of the target plant 100. In the following, when there is no need to distinguish between the multiple backlash portions BL1 and BL2, the subscripts will be omitted and they will be referred to as "backlash portion BL." Also, the k-th backlash portion counting from the motor 102 will be referred to as "backlash portion BL k " The same applies to other elements.

[0019] The backlash portion BL is a portion where a gap or deflection occurs when the driving direction is reversed. BLk is the backlash part BL k This is the amount of gap or deflection between the load and the shaft. Due to the presence of this backlash portion BL, when the drive direction is reversed, a dead zone where no movement is transmitted to the load side temporarily occurs, i.e., backlash occurs. This backlash causes a command tracking error. To illustrate this, in Figure 2, the moment of inertia J Lk and backlash part BL kThe figure shows a model consisting of only

[0020] As described above, the position control device of this example is used for axis control of a numerically controlled machine or robot. Typically, a first load end that drives in a first axial direction and a second load end that drives in a second axial direction are connected to the axis to be controlled. The first and second load ends are then driven sinusoidally with a phase difference of 90 degrees from each other, thereby driving the axis to be controlled in an arc. The following describes an example in which the load end 104 is driven sinusoidally to drive the axis to be controlled in an arc. When the load end 104 is driven sinusoidally, the position command value X is expressed by Equation 1 using the radius R0 of the arc, the offset X0 of the center of the arc, the angular velocity ω0, and the time t. X=X0+R0×sin(ω0t) =X0+R0×sinθ Equation 1

[0021] The position control device is physically a computer having a processor and a memory. Such a position control device may be configured, for example, by combining multiple physically separated computers. Furthermore, the position control device may be configured, for example, as a numerical control device.

[0022] The position control device functions as a torque command value τ m The position control loop section 20 receives a position command value X from a higher-level device. The position control loop section 20 also receives a load position detection value X L and motor position detection value X m Load position detection value X L is a position detection signal provided at the load end 104. Also, the motor position detection value X m is a signal obtained by converting the signal of the rotation angle detector installed on the motor 102 into a linear distance.

[0023] The position command value X is the backlash compensation value X output from the backlash compensation unit 21. BLcis added and compensated. The position command value after compensation X c is time-differentiated by a differentiator 51 to obtain the velocity feedforward amount V fc The subtractor 50 calculates the compensated position command value X c to position feedback value X f The position error er is output. f The calculation of will be described later. Position error amplifier 52 amplifies position error er by a factor of position loop gain Kp. The outputs of differentiator 51 and position error amplifier 52 are added together in adder 54 to become a velocity command. Converter 60 converts this velocity command into an angular velocity to generate an angular velocity command value ω m * Output.

[0024] Motor position detection value X m is time-differentiated by a differentiator 56, and is further converted into the motor speed ω m The subtractor 55 converts the speed command value ω m * to motor speed ω m The speed error is multiplied by Gv (proportional integral amplification is generally used) in the speed error amplifier 57, and the torque command value τ m is output as

[0025] Position feedback value X f is the load position detection value X L Motor position detection value X m The detected value deviation ΔX obtained by subtracting BLc More specifically, the load position detection value X L Motor position detection value X m is subtracted to calculate the detected value deviation ΔX. Then, the backlash compensation value X is applied to this detected value deviation ΔX. BLc The sum is subjected to low-pass filtering by the LPF processing unit 17. The output value of the LPF processing unit 17 and the motor position detection value X m and are added together to form the position feedback value X f Position feedback value Xf The reason for calculating in this way will be described later.

[0026] Next, the backlash compensation unit 21 will be described. Prior to describing the detailed configuration of the backlash compensation unit 21, the behavior of the target plant 100 when the drive direction is reversed will be described. FIG. 3 shows the relationship between the position command value X, the acceleration command value A, and the sliding friction torque τ F FIG. 10 is a diagram illustrating an example of a change in

[0027] As described above, in this example, a position command value X=X0+R0×sin(θ) that changes in a sinusoidal manner is input. In this case, the drive direction is reversed at the timings of θ=1 / 2π and θ=3 / 2π. The acceleration command value A is obtained by differentiating the position command value X twice. This acceleration command value A has a waveform with a phase difference of π with respect to the position command value X. Sliding friction torque τ F is the sliding friction torque required to drive the load.

[0028] In this case, backlash occurs in the ranges Sa and Sb around 1 / 2π and 3 / 2π. The load-side transmission torque τ Lk The change in will be described with reference to FIGS.

[0029] First, as shown in Fig. 5, consider the case where there is only one backlash portion BL1 in the torque transmission path 110. m denotes the moment of inertia of the motor 102, and J L1 indicates the moment of inertia from the backlash portion BL1 to the load end 104. In the example of FIG. L1 is the total moment of inertia J, which is the moment of inertia of the entire load L In addition, the load end 104 is subjected to a sliding friction torque τ F Hereinafter, the left direction of the paper will be called the "N direction" and the right direction of the paper will be called the "P direction."

[0030] The backlash part BL1 is the output end OUT N and the output terminal OUT on the P side P In the example of FIG. 5, the input terminal IN has an output terminal OUT N while the output terminal OUT P Therefore, in the state of Figure 5, when moving in the N direction, the load position detection value X L is the motor position detection value X m is consistent with X L =X m On the other hand, when the movement direction is reversed and the motor 102 moves in the P direction, the backlash amount X BL1 That is, X L =X m +X BL1 It is necessary to do so.

[0031] Therefore, at the timing when the direction of travel of the position command value X is reversed, the velocity feedforward amount V fc , the backlash speed V BL It is possible to compensate for the backlash velocity V BL For example, V BL =V BL0 ×e -t÷T The area of ​​the impulse response time function with time constant T is the backlash amount X BL1 This backlash velocity V BL When the direction of travel reverses, the velocity feedforward amount V fc It is possible to add or subtract from

[0032] However, in order to ensure high tracking performance even after the direction of movement is reversed, the load-side transmission torque τ L1 At the reversal timing, the backlash amount X BL1 The motor operation must be performed quickly. L1 is the backlash part B L1 When the second derivative of the position command value X is the acceleration command value A, the load-side transmission torque τL1 is expressed by the following equation 2. τ L1 =J L1 ×A+τ F formula 2

[0033] In addition, the sliding friction torque τ F The absolute value of is constant regardless of the speed, and the sign is reversed when moving in the P direction and when moving in the N direction. That is, the sliding friction torque τ F is expressed by Equation 3. In Equation 3, τ FP is a predetermined fixed value, and sgn(i) is a sign function that outputs 1 when the argument i is positive, -1 when the argument i is negative, and 0 when the argument i is 0. τ F =sgn(V)×τ FP formula 3

[0034] To maintain high tracking performance, the load-side transmission torque τ expressed by Equation 2 L1 It is necessary to compensate the command value according to the state of τ. FIG. 6 is a schematic diagram showing the state of change of the position command value X and torque in the target plant 100 of FIG. 5. In the example of FIG. 6, τ F =J L1 × A is established, the load side transmission torque τ L1 This is the timing when the signal is reversed.

[0035] Here, if there is only one backlash part BL, J L =J L1 Furthermore, the total moment of inertia J L is the motor moment of inertia J m (constant value) and real-time acceleration / deceleration characteristics, it can be easily identified online. F is measured or identified in advance. Therefore, when there is only one backlash portion BL, the load side transmission torque τ L1 The state of the load is the total moment of inertia J L , acceleration command value A, and sliding friction torque τ F It can be easily determined from the

[0036] On the other hand, as shown in FIG. 2, when there are a plurality of backlash portions in the torque transmission path 110, the load-side transmission torque τ L1 ,τ L2 The backlash compensation value X is set according to the result of each judgment. BLc In other words, when there are multiple backlash portions, the load-side transmission torque τ of one backlash portion BL1 obtained by the above-mentioned formula 2 must be changed. L1 The appropriate backlash compensation value X cannot be obtained by simply monitoring BLc As a result, high command follow-up performance cannot be maintained. Therefore, in this example, a plurality of backlash portions BL k Load side transmission torque τ Lk The principle of backlash compensation in this example will now be described.

[0037] First, referring to Fig. 2, a case where a plurality of backlash portions BL1, BL2 exist in the torque transmission path 110 will be described. Although Fig. 2 shows only two backlash portions BL, the following description will be given assuming that there are n backlash portions BL. In addition, the k-th backlash portion BL, which is located k-th from the motor, will be described below. k and the next backlash part BL k+1 (Backlash part BL k+1 If there is no inertia, the moment of inertia between the load end 104) is the "kth part moment of inertia J Lk " Also, the kth backlash part BL k The k-th load-side transmission torque τ Lk Furthermore, the sliding friction torque τ F are all sliding friction torques at the load end 104.

[0038] k-th load-side transmission torque τ Lk can be expressed by the following equations 4 and 5. τ Lk =M k ×A+τ F formula 4 M k =J Lk +J Lk+1 +···+J Ln formula 5

[0039] Therefore, in the example of Figure 2, the first load side transmission torque τ L1 and second load side transmission torque τ L2 are expressed as Equation 6 and Equation 7, respectively. τ L1 =(J L1 +J L2 )×A+τ F =J L ×A+τ F formula 6 τ L2 =J L2 ×A+τ F formula 7

[0040] Next, the backlash compensation value X BLc Let us consider the case where a sinusoidal position command value X is input with θ set to 0 (i.e., backlash compensation is turned off). In this case, the position command value X is expressed as X = X0 + R0 × sinθ. Here, when θ is less than θ1 in FIG. 4, the position command value X advances in the N direction, but the first load-side transmission torque τ L1 is less than 0. Therefore, the input end IN of the first backlash portion BL1 is connected to the output end OUT N In other words, the input terminal IN is in contact with the output terminal OUT. N Gap X S1 is 0.

[0041] After that, when θ>θ1, the first load-side transmission torque τ L1 >0. As a result, the input terminal IN becomes the output terminal OUT P The motor 102 drives extra so that the gap X S1 is the amount of backlash X BL1 If the load position detection value X is less than 1 / 2, the torque is not transmitted to the end side from the first backlash portion BL1. Lwill overshoot in the N direction relative to the position command value X. As a result, as shown in the third row of FIG. 4, immediately after the angle θ1, the position deviation DIF=XX L will increase rapidly.

[0042] Similarly, at the second backlash portion BL2, the second load-side transmission torque τ L2 The position error DIF increases sharply immediately after the angle θ2 at which the value of O The sudden increase in the position deviation DIF at F This is a delay in response to a sudden change in the speed, and is not a delay in response caused by backlash.

[0043] In order to suppress the sudden increase of the position deviation DIF caused by the backlash, the timing at which the position deviation DIF suddenly increases, that is, the timing at which the k-th load-side transmission torque τ Lk When the sign of changes, the backlash compensation value X is added to the position command value X. BLc The kth backlash part BL k Backlash amount X BLk In a more generalized explanation, the k-th backlash portion BL k The compensation value X corresponding to BLck is expressed as Equation 8.

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[0044] In addition, the backlash compensation value X is added to the position command value X. BLc is a multiple backlash part BL k Each compensation value X BLck That is, the backlash compensation value X BLc is expressed as Equation 9. X BLc =X BLc1 +X BLc2 +···+X BLcn formula 9

[0045] As is clear from the explanation so far, the backlash compensation value XBLc In order to calculate the backlash, k Load side transmission torque τ Lk However, it is necessary to know the sign (i.e., positive or negative) of the load-side transmission torque τ Lk To determine the sign of the coefficient M in Eq. k It is necessary to know the value of the coefficient M k As shown in Equation 5, the corresponding backlash part BL k is the moment of inertia from the load end 104 to the load side transmission torque τ Lk is a coefficient for detecting inversion of

[0046] The coefficient M k In this example, in order to grasp the backlash compensation value X before the target plant 100 is operated normally, BLc In this state, the target plant 100 is temporarily operated with the position command value X of Equation 1 that changes in a sinusoidal waveform, as described above. Lk The timing when the sign of the angle θ1,θ2,...,θ n The position deviation DIF increases sharply.

[0047] Here, the load side transmission torque τ at angle θ1 L1 is the angle θ k Load side transmission torque τ Lk Therefore, the angle θ1,θ k The acceleration command value A at each k In this case, the following equation 10 holds: M1×A1+τ F =M k ×A k +τ F M1×A1=M k ×A k Formula 10

[0048] In addition, the acceleration command value A is the value obtained by differentiating the position command value X=X0+R0×sin(θ) twice, so A=-R0ω0 2 ·sin(ω0t)=-R0ω0 2·sin(θ). Furthermore, M1 is the total moment of inertia J L Therefore, Equation 10 can be transformed into Equation 11. J L ×(-R0ω0 2 ·sin(θ1))=M k ×(-R0ω0 2 sin(θ k )) M k =(sinθ1 / sinθ k )×J L Formula 11

[0049] As is clear from Equation 11, the coefficient M k is the angle θ indicated by the position command value X when the position deviation DIF suddenly increases during trial operation. k and the total moment of inertia J L Therefore, in this example, before the normal operation of the target plant 100, a trial operation is performed, and the angle θ k Then, this angle θ k and the total moment of inertia J L Applying Equation 11 to the multiple backlash parts BL k The corresponding coefficient M k Calculate the calculated coefficient M k is stored in the reversal detection unit 12 as a coefficient for reversal detection. When the target plant 100 is operated normally, this coefficient M k Based on this, the load side transmission torque τ Lk The sign of the backlash compensation value X BLc Calculate.

[0050] Next, the configuration of the backlash compensation unit 21, which is constructed based on this principle, will be described. As shown in FIG. 1, the backlash compensation unit 21 has a coefficient calculation unit 10, a reversal detection unit 12, and a compensation value calculation unit 13. When the calculation flag Ftun is ON, the coefficient calculation unit 10 calculates the above-mentioned coefficient M k The calculation flag Ftun is also input to the compensation value calculation unit 13, and when the calculation flag Ftun is ON, the compensation value calculation unit 13 calculates the backlash compensation value XBLc In other words, when the calculation flag Ftun is ON, backlash compensation is turned OFF.

[0051] The coefficient calculation unit 10 calculates the position command value X and the load position detection value X input when Ftun=ON. L , and the total moment of inertia J L Based on the coefficient M k Specifically, the coefficient calculation unit 10 calculates the position command value X and the load position detection value X L Then, at the timing when the position deviation DIF suddenly increases, the angle θ indicated by the position command value X is calculated. k The timing of the sudden increase in the position error DIF may be determined, for example, from the time differential value of the position error DIF. In other words, the timing at which the time differential value of the position error DIF exceeds a specified threshold value may be determined as the timing at which the position error DIF suddenly increases.

[0052] Multiple backlash parts BL k The corresponding angle θ k If the angle θ k and the total moment of inertia J L and apply Equation 11 to obtain the coefficient M k Calculate the backlash part BL k The corresponding coefficient M k Once these coefficients M k to the inversion detection unit 12. In addition, a plurality of coefficients M k is calculated, the calculation flag Ftun is switched from ON to OFF, and backlash compensation is turned ON. Note that the calculation flag Ftun may be switched automatically according to the calculation state in the coefficient calculation unit 10, or may be switched manually by an operator.

[0053] The inversion detection unit 12 uses a plurality of coefficients M k Based on the multiple backlash part BL k Load side transmission torque τ in each LkSpecifically, the reverse detection unit 12 receives a velocity command value V obtained by first differentiating the position command value X, an acceleration command value A obtained by second-order differentiating the position command value X, and a sliding friction torque τ F In normal operation with backlash compensation turned on, the position command value X is not limited to a sine wave command, and position command values ​​X for various movements are input. The reverse detection unit 12 detects the position of a plurality of backlash portions BL k Load side transmission torque τ in each Lk is calculated based on Equation 4. The obtained load-side transmission torque τ Lk The discrimination signal SN obtained by applying the sign function to k =sgn(τ Lk ) to the compensation value calculation unit 13. As described above, the sign function sgn(i) is a function that outputs 1 when the argument i is positive, outputs -1 when the argument i is negative, and outputs 0 when the argument i is 0.

[0054] The compensation value calculation unit 13 calculates the backlash compensation value X BLc The compensation value calculation unit 13 outputs a plurality of backlash portions BL k Each backlash amount X BLk Here, as described above, when the calculation flag Ftun is ON, the compensation value calculation unit 13 stores X BLc On the other hand, when the calculation flag Ftun is OFF, the compensation value calculation unit 13 calculates the backlash compensation value X BLc In Equation 8, SN k If >0, then X BLck =X BLk and SN k If ≦0, then X BLck =0.

[0055] The backlash compensation value X output from the compensation value calculation unit 13 BLc is added to the position command value X, and the compensated position command value X c Then, this compensated position command value X c Based on this, the velocity feedforward amount V fcBy calculating the velocity feedforward amount V fc , the backlash speed compensation value V BLc As a result, multiple backlash portions BL k Even if there is a problem, high position tracking performance can be maintained.

[0056] Also, as shown in FIG. 1, in this example, the load position detection value X L and motor position detection value X m The deviation from the detected value (detection value deviation ΔX) is the backlash compensation value X BLc Add the above and the detected value deviation after compensation ΔX c Furthermore, the post-compensation detection value deviation ΔX c and the motor position detection value X m and are added together to obtain the position feedback value X f Calculate.

[0057] Here, if the output of the LPF processing unit 17 is expressed as α times the input (where 0≦α≦1), the position feedback value X f can be expressed by Equation 12. X f =α{(X L -X m )+X BLc}+X m =X L +(1-α)(X m -X L )+α×X BLc Formula 12

[0058] where (X m -X L ) and X BLc If and are equal, then X c =X m and X c =X L +X BLc , that is, X=X L Thus, according to the position control device of this example, the backlash compensation value X is added to the position command value X. BLc Compensated position command value Xc Even if a fully closed position control system is configured with the input, the load position detection value X L is the backlash compensation value X BLc There is no physical shift due to this.

[0059] Furthermore, in this example, the backlash compensation value X BLc is applied to the position command value X, not the speed command value. Therefore, the response error of the speed control system can be compensated for by the response operation of the position control system. As a result, at each portion where an in-backlash operation occurs, the load position detection value X of the target plant 100 L The tracking error for the position command value X can be reduced.

[0060] Next, another embodiment will be described. In the above description, the load-side transmission torque τ Lk Based on the calculation results, multiple backlash parts BL k The corresponding compensation value X BLck However, the compensation value X BLck When determining the switching timing of the load side transmission torque τ Lk There is no need to calculate .

[0061] That is, by substituting Equation 3 and Equation 11 into Equation 4, the load side transmission torque τ Lk can be transformed into Equation 13. τ LK =J L (sinθ1 / sinθ k )×A+τ FP ×sgn(V) Equation 13

[0062] Here, the backlash compensation value X BLc When the target plant 100 is temporarily operated in the state of θ = 0, the first load side transmission torque τ L1 = 0. The velocity command value V1 at this angle θ1 is V1 = R0 × ω0 × cosθ1, and the acceleration command value A1 is A1 = -R0 × ω0 2× sinθ1. Substituting these equations into equation 13 gives equation 14.

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[0063] Furthermore, rearranging equation 14 gives equation 15.

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[0064] Substituting this equation 15 into equation 13 and rearranging it, equation 16 is obtained.

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[0065] where τ FP is a predetermined fixed value, and its sign is always positive. Therefore, the load side transmission torque τ Lk The determination of the sign of is performed by using the determination parameter r Lk This is the same as determining whether a number is positive or negative.

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[0066] where A k =-R0×ω0 2 ×sinθ k From Figure 4, sgn(ω0cosθ1)=sgn(V1)=sgn(V k ) Substituting these into equation 17 and rearranging, we obtain equation 18.

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[0067] Then, the determination parameter r shown in Equation 18 Lk The timing at which the positive and negative signs of the k Each load side transmission torque τ LkThis may be considered as the timing when the sign of the signal is reversed.

[0068] In this case, the coefficient calculation unit 10 calculates the coefficient N k is calculated and output to the inversion detection unit 12 as a coefficient for inversion detection. N k =sgn(V k ) / A k formula 19

[0069] In addition, the inversion detection unit 12 calculates the determination parameter r Lk Furthermore, the inversion detection unit 12 calculates the determination parameter r Lk Applying the sign function to the discriminant signal SN k =sgn(r Lk The compensation value calculation unit 13 outputs the discrimination signal SN k Depending on the backlash compensation value X BLc Change the

[0070] Even in this case, the load side transmission torque τ Lk The timing of the reversal of the backlash compensation value X can be accurately determined. BLc As a result, the backlash portion BL k Even if there is a problem, high position tracking performance can be maintained.

[0071] The configurations described above are merely examples, and other configurations may be changed as long as the configuration of claim 1 is included. For example, the backlash portion BL k The number of the position feedback value X is not particularly limited as long as it is 2 or more. f The calculation method of the position feedback value X may also be changed. For example, in the example of FIG. f The motor position detection value X m However, as shown in FIG. 7, the motor position detection value X m is the position feedback value X f It may be configured so that the information is not input to the [Explanation of symbols]

[0072] 10 Coefficient calculation unit, 12 Inversion detection unit, 13 Compensation value calculation unit, 17 LPF processing unit, 19, 60 Converter, 20 Position control loop unit, 21 Backlash compensation unit, 50, 55 Subtractor, 51, 56 Differentiator, 52 Position error amplifier, 54 Adder, 57 Speed ​​error amplifier, 100 Target plant, 102 Motor, 104 Load end, 110 Torque transmission path, 120 Current control unit, A Acceleration command value, BL Backlash unit, DIF Position error, Ftun Calculation flag, IN Input end, J L Total moment of inertia, J Lk kth partial moment of inertia, J m Motor moment of inertia, M k ,N k Coefficient, OUT N Output terminal, OUT P Output terminal, SN k Discrimination signal, X Position command value, X BLc Backlash compensation value, X BLk Backlash amount, X L Load position detection value, X c Compensated position command value, X f Position feedback value, X m Motor position detection value, τ F Sliding friction torque, τ Lk k-th load side transmission torque, τ m Torque command value.

Claims

1. A position control device for a target plant in which a motor and a load end are connected via a torque transmission path having a plurality of backlash portions, a coefficient calculation unit that performs a provisional operation of the target plant so as to reverse the traveling direction with backlash compensation turned off, and calculates a coefficient for reversal detection for each of the plurality of backlash portions based on the position command value at a timing when a position deviation between the position detection value and the position command value at the load end suddenly increases, or based on the speed command value and the acceleration command value at the timing when the position deviation suddenly increases; a reversal detection unit that operates the target plant with the backlash compensation turned on, and detects timings at which the load-side transmission torque at each of the plurality of backlash portions reverses based on the reversal detection coefficient, the position command value, and the moment of inertia of the entire load; a compensation value calculation unit that stores in advance the amount of backlash for each of a plurality of backlash portions and increases or decreases a backlash compensation value based on the amount of backlash corresponding to the backlash portion where torque is reversed at each timing when the load side transmission torque is reversed; a position control loop unit that controls the position of the motor so that the position detection value at the load end becomes a position command value after being corrected by the backlash compensation value; A position control device comprising:

2. 2. The position control device according to claim 1, wherein the compensation value calculation unit adds or subtracts the backlash amount of the k-th backlash portion, counting from the motor, to or from the current backlash compensation value at a timing when the load-side transmission torque reverses at the k-th backlash portion.

3. 3. The position control device according to claim 2, the position control loop unit controls the position of the motor so as to reduce an absolute value of a position error, which is a difference between a compensated position command value and a position feedback value; the position feedback value includes a sum of the load end position detection value and the backlash compensation value; A position control device characterized by:

4. 2. The position control device according to claim 1, The position command value in the provisional operation is X=X ０ +R ０ × sinθ, The coefficient calculation unit calculates θ when the position deviation increases suddenly due to the k-th backlash portion counted from the motor as θ ｋ The moment of inertia of the entire load is J Ｌ In this case, the coefficient M corresponding to the k-th backlash portion is ｋ A, M ｋ = (sinθ １ / sinθ ｋ ) x J Ｌ Calculate based on A position control device characterized by:

5. 5. The position control device according to claim 4, The compensation value calculation unit calculates the load-side transmission torque at the k-th backlash portion as τ Ｌｋ , the sliding friction torque is τ Ｆ , when the acceleration command value is A, τ Ｌｋ =M ｋ ×A + τ Ｆ In the equation, the load side transmission torque τ Ｌｋ A position control device characterized by calculating

6. 2. The position control device according to claim 1, The position command value in the provisional operation is X=X ０ +R ０ × sinθ, The coefficient calculation unit calculates an acceleration command value when the position deviation increases suddenly due to the k-th backlash portion counted from the motor as A ｋ Then, the coefficient N corresponding to the k-th backlash portion is ｋ , N ｋ = sgn(V ｋ ) / A ｋ Calculated based on the formula: A position control device characterized by:

7. 7. The position control device according to claim 6, The compensation value calculation unit calculates a determination parameter r when the speed command value is V, the acceleration command value is A, and the sign function is sgn. Ｌｋ , r Ｌｋ = -A x N ｋ +sgn(V), and the determination parameter r Ｌｋ and detecting a timing when the positive and negative signs of the signal k are reversed as a timing when the load-side transmission torque at the k-th backlash portion is reversed.

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